Continuous kiln



March 9, 1965 G. B. REMMl-:Y 3,172,547

CONTINUOUS KILN Filed March 26, 1963 5 Sheets-Sheet l ATTORNEYS March 9, 1965 c5. B. REMMEY 3,172,647

CONTINUOUS KILN Filed March 26, 1965 5 Sheets-Sheet 2 Fl G. 3.

. INVENTOR GEORGE BIGKLEY REMMEY ATTORNEYS March 9, 1965 G. B. REMMEY 3,172,647

CONTINUOUS KILN Filed March 26, 1963 5 Sheets-Sheet 5 F I G. 4.

INVENTOR ZIB ZZOGEORGE BICKLEY REMMEY Z J VL ATTORNEYS United States Patent vOce 3,172,647 Patented Mar. 9, 1965 3,172,647 CONTINUUS KILN George Bickley Remmey, Lienkintown, Pa., assignor to Bickley Furnaces, Incorporated, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 26, 1963, Ser. No. 268,203 13 Claims. (Cl. 263-28) This invention relates to a ring system for a continuous kiln or the like and is applicable to other continuous heattreating furnaces.

Continuous kilns in use heretofore have several disadvantages involved in their tiring systems. For example, prior continuous kilns have been unable to achieve a predictable and settable temperature in zones along the length of the kiln. Accordingly, prior continuous kilns are not adjustable with accuracy to various heating cycles and require considerable time in placing them into operation and in adjustment of the tiring system during operation. It is one object of this invention to provide a firing system which is settable to achieve and maintain desired temperatures in zones along the length of a continuous kiln.

One of the reasons for the inability for conventional kilns to obtain controllable temperature zones is that these kilns employ the counterliow principle wherein a current of air is moved continuously through the kiln in the direction opposite to the movement of the Ware through the kiln. This longitudinal flow creates a condition that does not permit temperature adjustment along the longitudinal zones of the kiln and results in i'uel inefficiency. It is an object of this invention to provide a firing system for continuous kilns or the like in which air flow between the zones is minimized whereby the kiln temperatures may be adjusted with accuracy.

Another problem involved in conventional kilns is the uneven temperature distribution in the kiln chamber caused by the hot gases stratifying along the upper portion of the kiln chamber as a result of their buoyancy. This problem is accentuated in the heating up and cooling down regions wherein considerable temperature dilerentials exist between the top and bottom of the kiln chamber. In most cases, this temperature diterential is several hundred degrees and often more. Accordingly, the ware on top of the kiln is considerably hotter than the ware at the bottom. This requires that at a critical temperature range of the ware the necessary slow heating rate must be extended from the time the high temperature ware passes through the critical temperature range to include the time for the low temperature v/are to also pass through this critical temperature range. This results in the necessity for increasing the length of time the ware passes through the kiln. Another object of the invention is to provide a tiring system for a continuous kiln in which there is maintained a substantially constant temperature throughout the height of each zone of the kiln whereby time savings are achieved.

A further object of the invention is to provide a firing system for continuous kilns in which there is achieved good circulation throughout each temperature zone so that effective heat transfer may take place between the gases and the ware.

The above and other objects and features of the invention will appear more fully from a consideration of the following detailed description in conjunction with the accompanying drawings wherein:

FIGURES lA, 1B and 1C are longitudinal sectional views of adjacent sections of a continuous kiln in accordance with this invention;

FIGURE 2 is a section taken on line 2 2 of FIG- URE 1B;

FIGURE 3 is a section taken on line 3 3 of FIG- URE 1B;

FIGURE 4 is a section taken on line 4-4 of FIG- URE 1C; and

FlGURE 5 is a sectional View of a burner assembly used in the kiln in accordance with this invention.

The continuous kiln in accordance Wit-h this invention comprises a horizontally extending structure defining a longitudinal tunnel or kiln chamber 2li defined by aA lining of suitable refractory material. The chamber defining refractory walls include an arched ceiling 22 supported on vertical side walls 24 and 26. The type and the size of the refractory at various locations of the kiln is chosen in accordance wi-th the particular temperature occurring in zones within the kiln chamber 20 at such locations. Preferably the lining consists of prefired burner blocks and bricks of a high purity sintered mullite composition and is backed up with a layer of insulating brick which, in turn, is backed up with insulating block. The refractory walls are supported in a steel plate casing 28 with welded structural steel reinforcement. The kiln chamber is supported above the door level and steel cross-members 3! are provided to tie the bottom of the kiln together and to support rails for the kiln cars. The structural aspects of the kiln are in accordance with conventional practice and will be apparent to those skilled in the art.

The bottom of the kiln chamber 20 is dened by refractory walls 32 supported on the kiln cars 34. The cars ride on horizontally extending rails andare provided with conventional sand sealing means 35 for closing the kiln chamber at the bottom thereof. A vertically sliding door 36 is provided at the inlet of the kiln to close lthe same when necessary. A baille 37 is provided at the outlet of the kiln. The balile is constructed to close oli the outlet end of the kiln and has a central opening sized to permit movement of the kiln cars through the outlet end of the kiln. The car-s 34- are moved through the kiln by any suitable means well known in the art, as for example, a hydraulic pusher. The cars 34 are provided with a horizontal platform 38 for supporting the ware indicated at W. The ware supporting structure is provided with transversely extending openings 39 to permit circulation of the hot gases as will be described more fully hereafter.

The kiln consists of a plurality of individual zones or ring sections l-S throughout its length, each section extending an equal longitudinal distance. Means are provided at each section for producing a settable predetermined temperature therein. By Way of a typical example, a kiln for 3l00 F. iring of a ware setting or size of eighteen inches by eighteen inches may comprise firing sections extending four feet along the kiln chamber.

The individual tiring sections 1 to 6 comprise a heatup zone in which the temperature of the Ware is raised under controlled conditions. The liring sections 7 and 8 comprise a soak zone in which the ware is heated to the maximum temperature for the heating cycle. Firing sections 9 and 10 comprise a pre-cool zone in which the ware is cooled rapidly to lower the temperature beneath the soak temperature. Firing sections 11 to 15 comprise a cooling zone in which the ware temperature is gradually reduced by the use of cooling air. The number of individual firing sections comprised in each of the composite zones may be varied in accordance with the particular kiln application.

The means for producing a predetermined settable ternperature in each individual zone comprises a pair of burner or nozzle assemblies for introducing gas into the kiln chamber tangentially at the top and at the bottom thereof as is best shown in FIGURES 2, 3 and 4. These gas introducing means are arranged in the same vertical plane centrally of the zone and to direct gases into the klin chamber tangentially in the same circumferential direction by way of tangentially extending inlet nozzle passages 21. While in accordance with the broadest aspect of the invention various gas introducing means may be used, it is preferable to use a burner assembly such as that disclosed in U.S. vPatent No. 3,055,652. The advantage of using such a burner assembly is that this apparatus is designed to maintain a sufficient gas stream mass velocity so that all the gases introduced into the zone circulate around the kiln.The introduced gases sweep continuously from top to bottom around the ware as is 'shown by the arrows in FIGURES 2, 3 and 4. The passages 39 in the supporting structure of the kiln cars 34 permit passage of the gases across the bottom of the kiln chamber 20.

The velocity of gas streams should be set slow enough so that the ware is not disturbed and high enough to make a few revolutions around the kiln chamber each second. rIhis full time high velocity gas circulation eliminates stratification of the gases and avoids Vany substantial temperature differential between the top and bottom of the kiln chamber.

Since the above-mentioned patent discloses the details of the burner assembly for achieving the desired results, only a brief description of this burner assembly will appear herein. As shown in FIGURE 5, each burner assembly 40 comprises a suitable burner 41 adapted to be mounted on the shell of the kiln. The burner 41 comprises a body 42 cemented to a refractory block 48defining a combustion tunnelSt communicating with the interior of the body 42. Preferably the burner 41 is of the type having a plug defining an annular burner port as is more fully described in said patent. A rectangular diffusion air block 70 of refractory material is positioned in a rectangular lopening 72 in the vertical side wall of the kiln. Block 79 has a recess 74 adapted to receive the downstream end of block 48. Block 70 has 'a central cavity 76 adjacent the upstream end of recess 74 and a bore 78 communicating with the downstream end of central cavity 76. Cavity 76 and bore 78 define a passageway through which the products of combustion from tunnel 50 pass and leading to the inlet nozzle passage 21 communicating with the kiln chamber 20.

A ceramic conduit 80 is mounted in the refractory Wall and communicates at its downstream end with a passageway 82 formed in block 70. Passageway 82 communicates with central cavity 76. Conduit St) and passageway 82 provide a path for the flow of diffusion air into cavity 76 from the air supply conduits which are connected to the upstream Vends of the conduits 80. Since air is diused with the products of combustion from tunnel 50 in cavity 76, this cavity may be termed a diffusion chamber.

A cylindrical diffuser member 86 is mounted in central cavity 76 and defines, at the inner wall thereof, a passageway between tunnel d and bore Y 78. v The* Vinner Wall of diffuser member S6, tunnels() and bore '73 are all in alignment. 'Diffuser member 86 has a radially extending flange V88 which positions the diffuser member 86 within cavity 76 so that the diffuser member outer wall is spaced from the wall of cavity 76 whereby an annular chamber 99 is formed adjacent the diffuser member' outer wall. Diffuser member 86 has a plurality of radial openings 92 extending therethrough and circumferentially and longitudinally spacedv thereabout. Openings 92 serve to meter or control the amount of air passing from chamber 90 through the diffuser member 86 into the products of combustion passing from combustion. tunnel 5G of burner 41. Diffuser member` 86Yis made of a Ymaterial which can withstand extreme thermal shock and thermal stress, such as silicon carbide, silicon nitride, mullite, alumina or otherceramics. Y

In the firing of the kiln, a fuel-air mixture is supplied to the burners 41 through conduits [62, valves being provided for regulating the amount of fuel-air mixture pass- Ving to the burners 41. Air is supplied to conduits 80 through distribution connections which have valves connected therein for regulating the amount of air passing to the chambers 90. The regulating valves are adjusted to provide the desired flame temperature and the mass velocity of the gas stream passing from the burner assemblies. In order to insure that all of the ware is heated uniformly, the mass velocity of the gas stream passing from the burner assemblies are adjusted so that the gas stream completely encircles the ware. When preheated diffusion air is used, the fuel-air mixture comprises 20 to 33 percent pre-mixed air, the rest of the air being supplied through the diffusion passages. The kdiffusion air control has a minimum low flow rate so that the circulation pattern is maintained at all times, it being better to have inefficient gas burning than to have too low a mass velocity.

The products of combustion leave combustion tunnel 50 and pass into the central opening in diffuser member 86. The secondary air passes from conduit into annular chamber 9) from which the air passes through openings 92. Diffuser member 86 serves to meter the air and cause it to mix in small jets with the fully burned combustion products passing from the combustion tunnel 50. The diuser member 86 insures that there is a thorough mixture or diffusion of the air and the products of combustion by reason of the plurality of openings 2 which direct the small jets of air at right angles into the products of combustion. i

-In the heat-up zone, the gas introducing means of firing section 1 comprises what may be termed a nozzle assembly which introduces only hot air into this section of the kiln chamber 20. Although there are no burners provided in this firing section, each nozzle assembly may have a construction similar to the burner assembly shown in FIGURE 5 so that a burner may be added if desired. The firing sections 2 to 6 are provided with burner assemblies constructed as shown in FIGURE 2 which illustrates the arrangement of firing section 6. It is to be noted that in FIGURES 2, 3 and 4 the burner and nozzle assemblies are shown in outline form for simplicity of illustration. Each of the upper burner assemblies of firing sections 2 to 6 receives an air-gas mixture by way of a distribution connection 166 providing communication between the burner inlet conduit 62 and a manifold line 192. The manifold line 102 is connected to the inlet line 164 which receives a supply of the airgas mixture from a gas premixing machine (not shown). Each of the lower burner assemblies of firing sections 2 to 6 receives the air-gas mixture by way of a distribution connection 106 providing communication between the burner inlet conduit 62 and a manifold line 108. The manifold line 108 is connected to the inlet line 104 from the fuel supply. Each of the distribution connections 166 and 166 has connected therein a manually adjustable throttle valve which is set in accordance with the desired fuel input for a particular firing section.

Eachof upper and lower burner assemblies for firing sections 1 to 6 receives a supply of hot air by way of conduits Sti providing communication between the diffusion inlet passageways S2 and manifold ducts 110 and 112, respectively. The manifold ducts 11@ and 112 are connected to an inlet line 114 which is connected to the discharge conduit 116 of a hot air blower 118. The blower 11S draws hot air from the pre-cool zone as will be described hereafter. Each of the hot air conduits St) is provided with a manually adjustable throttle valve which is set in accordance with the desired hot air input for the particular firing section in accordance with the air-gas input.

Means are provided for exhausting gases from the heatup zone at various longitudinal locations of the kiln chamebr 29. Such means comprises a plurality of vcrtical conduits 120 communicating at their lower ends with the crown of the kiln chamber through ducts 121 and at their upper ends with a horizontally extending exhaust duct 122 communicating with the intake end of an exhaust blower 124. The discharge duct 126 of the blower or exhauster 124 may be connected to the outside of the building containing the kiln. Each of the vertical conduits is provided with a manually adjustable damper valve 12S for regulating flow therethrough. Two of the vertical conduits 12'!) communicate with firing section 1 and one of the conduits communicates with each of firing sections 2, 3 and 4. The exhaust conduits 120 closest to the charging end of the kiln draw gases at the lowest temperature of the heat-up zone so that a minimum amount of heat is removed from the kiln and maximum fuel emciency is achieved. The exhaust conduits 120 which are located toward lthe central region of the heat-up zone are located to make it possible to draw E gases from this zone before they cool enough to permit condensation of alkalies or other volatile materials within the zone.

Control means are provided for maintaining automatically a desired temperature in the heat-up zone. Such means comprise a pyrorneter 130 arranged to sense the temperature in the heat-up zone and to actuate a suitable controller 132. The controller 132 operates control motors 134 and 136 which adjust throttle valves 138 and 14@ connected in the air-gas input manifolds 1h21, 198 and the hot air intake line 114, respectively. ln operation, if the pyrometer senses a drop in temperature, the controller is actuated to effect an increase in the flow of airgas mixture and of the hot air into the supply lines for the burner assemblies. The controller may comprise suitable differential pressure transmitters and ratio relays for regulation of the air supply pressure as a function of the fuel supply pressure. The specific details of the control means is in accordance with techniques well known in the control art and will be readily apparent to those skilled in the art.

The construction of the tiring sections 7 and 8 forming the soak zone is illustrated by FlGURE 3 which shows firing section 7 in cross-section. rI'he upper burner assembly of firing section S receives the air-gas mixture by way of a distribution connection 142 providing communication between the burner inlet conduit 62 and a line 144 connected to the fuel inlet line 164. A manually adjustable throttle valve is connected in the distribution line 142 to regulate flow therethrough. The lower burner assembly of firing section 8 receives the gas-air mixture by way of a distribution connection 146 providing communication between the burner inlet conduit 62 and a line 148 connected to the fuel inlet line 104. A manually adjustable throttle valve is connected in the distribution line 146 to regulate flow therethrough.

Fthe upper burner assembly of firing section 8 receives a supply of hot air by way of a distribution conduit Sti providing communication between the diffusion inlet passageway S2 of the burner assembly and a duct 150. The duct S is connected to the discharge line 116 of the hot air blower 11S by connections 152 and 154. The lower burner assembly of firing section 8 receives a supply of hot air by way of a distribution conduit d@ providing communication between the diffusion inlet passageway S2 of the burner assembly and a duct 156. The duct 156 is connected to the discharge line 116 of the hot air blower 11d by connections 158 and 154. Manually adjustable throttle valves 16u are connected in the distribution conduits Si) to regulate flow therethrough.

The upper burner assembly of firing section 7 receives the air-gas mixture by -way of a distribution connection 152 providing communication between the burner inlet conduit 62 and a line 164i connected to the fuel inlet lineI 1li-i. A manually adjustable throttle valve is connected in the distribution connection 162 to regulate tlow therethrough. A similar air-gas mixture supply arrangement is provided for the lower burner assembly, this arrangement being omitted from the drawings for simplicity of disclosure.

The =hot air supply for the firing section 3 is identical to the supply for firing section 7 whereby corresponding parts have been given the same reference numerals with primes added. The connecting conduits receive the supply of hot air from the discharge 116 of the hot air blower from the supply line and deliver them to the distribution lines by Way of ducts formed in the kiln. Suitable manually adjustable throttle valves are provided for regulating lthe air flow to the burner assemblies.

Control means are provided for maintaining automatically a desired temperature in the soak zone. This control means involves two controlled zones, one in each of the tiring sections 7 and and comprises a pair of pyrometers 166 and 168 arranged to sense the temperature in firing sections 7 and 3, respectively, and to actuate a controller 179. The controller 170 may comprise suitable differential pressure transmitters and ratio relays for controlling the operation of motor operated valves 172 and 174 in the fuel supply lines 144- and 164, respectively, and motor operated valves 176 and 178 in the hot air supply lines 154 and 154', respectively. The lower burner asemblies of firing sections 7 and 8 also have their fuel supply lines controlled by motor operated valves responsive -to the controller 170. The controller 170 regulates the air supply manifold pessure as a function of the .air-gas manifold pressure to insure the proper ratio for full combustion at the various burner positions. Again, there will be maintained a minimum air supply to insure sutlicient mass velocity. rl`he controller 17@ is responsive to the temperatures sensed by the pyrometers to control the burner temperatures to achieve the desired temperature within the tiring section. In order to permit the Iuse of a single controller with two separate control loops, 4there may be employed a timer-operated switching relay which transfers input and output circuits to the controller at regular intervals. The details of the temperature control will be apparent `to those skilled in the art.

The hot air recirculating blower 118 draws air from the pre-cool zone by way of vertical conduits 1S@ con- .nected at their lower ends with the firing sections 9 and 10, respectively, and at their upper ends with a horizon- Itally extending blower intake duct 132. Manually adjustable throttle valves 184 are provided in the vertical conduits 184D for regulating flow therethrough.

The gas introducing means in the firing sections 9 and .10 of the pre-cool zone deliver only hot air into the kiln chamber. The upper nozzle assemblies receive hot air by way of the distribution conduits 186 providing cornrnunication between the inlet to the nozzle assembly and a manifold duct 188 receiving air from the discharge line 190 of a recirculating blower 192. The lower nozzle assemblies receive hot air from the discharge line 190 of the blower 192 by way of a manifold duct 194 and distribution lines 196. The distribution lines 186 and 196 have connected therein manually adjustable throttle valves for regulating flow therethrough.

In the cooling zone, the gas introducing means of each of the tiring sections 11 to 15 comprises nozzle assemblies which receive cooling air through a longitudinal inlet and warm air through a side inlet. The cool and Warm air mix in the diffusion chamber and the mixture is forced into the kiln chamber by way of the inlet nozzle passageway 21. This mode of operation is best illustrated in FIGURES 1C and 4.

The cooling air is delivered to a pair of horizontally extending manifold ducts 200 and 202 by way of the discharge duct 204 of a cooling air blower 206. The cool air in the manifold duct 2th) is delivered to the longitudinal inlet of the upper nozzle assemblies by distribution connections 208. Each of the distribution connections 208 has a manually adjustable throttle valve therein for regulating flow therethrough. The cooling air in the manifold duct 202 is delivered to the longitudinal inlet of the lower nozzle assemblies by the distribution connections 210 each of which has a manually adjustable throttle valve therein for regulating flow therethrough.

The warm air is delivered to the horizontally extending manifold ducts 188 and 194 on opposite sides of the kiln by way of a duct 212 connected to the discharge duct 190 of the warm air recirculating blower 3&2. The warm air in the front manifold duct ld is distributed to the side inlet of vthe upper nozzle assemblies by suitable distribution conduits 214 each of which has a manually adjustable throttle valve therein for regulating llow therethrough and distribution passage 216V in the kiln wall. The warm air in the rear manifold duct 194 is delivered to the side inlet ofthe lower nozzle assemblies by suitable distribution conduits 218 each of which has a manually adjustable throttle valve therein for regulating flow therethrough and by distribution passages 220 in the kiln wall.

The recirculating blower 192 draws warm air from the crown of the cooling zone by means of a vertical conduit 222 communicating at its lower end with the crown of section 13 and at its upper end with the intake duct 224 for the blower 192. As is best shown in FIG- URE 1C the blower 1*,2 recirculates warm air through the kiln chamber. The discharge duct t9@ of the blower has an outlet portion 226 which may be connected to driers or the like (not shown). The llow through this outlet portion 22.6 is regulated by a throttle valve 22S connected therein.

Means are provided to control the movement of gases through the kiln chamber so that there is a minimum of longitudinal movement of the gases, particularly between the soak and pre-cool zones. In this respect, the kiln in accordance with this invention differs radically from conventional kilns employing the counterllow principle. The control means comprises a pair of pressure controller units for maintaining the same pressure on either side of a baille 230 between the soak and pre-cool zones. The baffle 236 is constructed to block tlow between the sections S and 9 and has a central opening sized to permit Vmovement of the kiln cars through the kiln. One controller unit comprises a pressure controller 232 responsive to the pressure sensed by a pressure sensing means 234 and arranged Ito operate a control motor 236 for a damper valveV 238 in the outlet duct 126 of the exhaust blower 124. The pressure sensing means 234.l is mounted on a kiln to be responsive to the pressure in the soak zone side of the baille 23d. The other controller unit comprises a pressure controller 24) arranged to be responsive to a pressure sensing means 242 and to operate a control motor 244 for the damper valve 228 in the outlet duct 226 of the .recirculating blower 192. The pressure sensitive means 242 is mounted on the kiln to be responsive to .the pressure in the kiln chamber in the pre-cool zone immediately adjacent the battle 236.

The controller unit responsive to the soak zone pressure operates to adjust the amount of air drawn from the heatup zone to maintain a predetermined kiln pressure at the pressure sensing location. At the same time, the pressure controller unit responsive to the pressure in the pre-cool zone adjusts the amount of air drawn from the cooling Zone to maintain the same predetermined pressure in the pre-cool zone sensing location as that pressure maintained by the other controller unit. Accordingly, the pressure on each side of the baille 236i is equalized to thereby minimize any ilow of gases across what may be termed a static llow plane. This static tlcw plane is indicated by the lines A-A in alignment with the baille 230.

To illustrate the operation of the pressure control, let it be assumed that the temperature control for the heatup zone calls for more fuel and more preheated air in which case this additional preheated air is drawn from the pre-cool 'zone by the recirculating blower 118. This would create a reduction in pressure in the pre-cool zone which would be sensed by the pressure responsive means 242 in this zone. The pressure responsive means 242 then actuates the controller 24u to operate the damper valve 228 in a direction so that less air is exhausted from the cooling zone to the pre-cool zone. This movement restores the pressure balance to minimize any ilow across the static ilow plane. ln a like manner, the pressure control on the heat zone side operates, by adjusting the damper valve 238 in accordance with the pressure sensed by pressure responsive means 23d, to maintain the set pressure on the heat zone side of the static iiow plane to restore the pressure balance thereat. Y

t will be apparent that the tiring system in accordance with this invention is settable to achieve predictable temperatures in various zones along the length of the kiln. Moreover, the zone temperatures may be varied in accordance with a desired heating cycle for a particular ware. Each zone can be adjusted to any temperature level providing for slow or fast heating at any zone with a constant car speed. Since the temperature profile along the length of the kiln will be the same for the top and bottom, there being no stratitication of the gases, this prole can be adjusted to meet with accuracy the requirements of ware quality and low kiln furniture costs. ln regions midway between the locations of the burners of each tiring section there is some mixing between the gases from adjacent ring sections whereby there is a gradual transition in temperature between adjacent Firing sections. In adjusting the tiring sections of the kiln, the throttle valves controlling the gas inputs are adjusted manually to produce the desired temperature as measured by temperature measuring means. The temperature measurement may be by thermocouples permanently installed in the kilns in locations so that they measure the temperature of one of the burner assemblies or by a portable pyrometer having a thermocuple which could be inserted through suitable holes in the kiln. The thermocouple access holes are indicated at i7 and extend horizontally through the vertical walls of the kiln at a central location. The temperature sensed at the opposite side of the kiln chamber from each burner is used as the basis for adjustment of such burner. This adjustment is made for each of the burner assemblies of each tiring section. It desired, pyrometric controls could be installed to control all lifteen tiring sections or merely certain critical groups of sections. It is apparent that most of the ilring sections oi the kiln disclosed may be set to various temperatures within a range of temperatures. Ot course, all of the tiring sections niay be provided with such control it desired.

Stratication of the hot gases is avoided by setting the air and fuel dow rates into the burner assemblies so that the mixture of gases entering the kiln chamber have a suilicient mass velocity to overcome the buoyancy tendency of the hot gases. The gas streams enter the kiln chamber with sumcient velocity to maintain rapid circulation which results in uniform temperatures from top to bottom in each tiring section.

During operation ot the kiln, the various blowers direct gases into appropriate ring sections through nozzle or burner assemblies. The cooling air supplied by the blower 296 is circulated around the ware in the cooling zone and moves gradually toward the soak zone. A portion of the air supplied by blower 2% is withdrawn by blower 192 and is delivered to driers by way ot outlet conduit 22.5 and the remaining portion of this air enters the intake l2 of blower liti. The baille 239 between the soak zone and the pre-coolin I zone in conjunction with the pressure controller units discussed above minimize movement of the air in the pre-cool and cooling zones into the soak zone which is the high temperature zone of the kiln. This results in increased thermal efficiency since any cooling gases moving into the soak zone would exert a cooling effect.

The blower 113 delivers hot air to the burner assemblies in the heat-up and soak zones. The amount of air discharged through cach burner assembly is regulated by the throttle valves associated therewith. A partial mixture of gas and air is burned in each burner to raise the temperature of the mixture ot burner combustion products and hot air to the desired level. The mixing takes place in the dkiusion chamber or" each burner assembly and the discharging gas streams from the burner' nozzles 21 sweep tangentially around the kiln chamber walls and circulate through the ware.

The gases introduced into the heat-up and soak zones sweep around the cars at right angles to the car movement and move gradually toward the entrance end of the kiln where these gases are exhausted by the blower 126i. The blower 124 draws the gases through the conduits 12@ and operates to withdraw gases at a temperature to prevent condensation of the alkalies and the like in the kiln chamber. lf desired, the dampers 12S in the conduits 120 may be positioned to cause movement of the gases all the way to the entrance end of the kiln chamber, this arrangement achieving maximum thermal eiciency.

Automatic temperature control of the heat-up and soak zones is accomplished by operation of the control means discussed above. Briey stated, this control is obtained by automatic adjustment of the amount of fuel and, through suitable interconnecting proportioning relays, the amount of hot air input.

it will be apparent that changes may be made in the construction and arrangement of parts Without departing from the scope of the invention. For example, a kiln which is to operate at lower temperatures would not require the particular heat-up zone disclosed and the ng sections of this zone could be replaced by a blower supplying room temperature air to the burners. In this case the exhaust from the pre-cooling zone would be connected to the intake of the recirculating blower 192 for the cooling zone whereby the cooling zone encompasses the pre-cooling zone. Accordingly, it is not desired to be limited except as required by the following claims.

What is claimed is:

l. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone defined by a second longitudinal portion of said wall means and comprising at least one tiring section extending longitudinally of the kiln chamber, each of said firing sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, and means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range oi' temperatures whereby each of said firing sections along the length or" said kiln chamber may be set to provide a desired temperature condition within said kiln chamber at the tiring section location.

2. A continuous kiln comprising wall means dening a horizontally extending kiln chamber, a heat-up zone defined by a rst portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent tiring sections extending longitudinally of the kiln chamber, a soak zone deiined by a second longitudinal portion of said wall means and comprising at least one tiring section extending longitudinally of the kiln chamber, a cooling zone between said soak zone and the discharge end of the kiln chamber, said cooling zone being dened by a third longitudinal portion of said wall means comprising a plurality of adjacent tiring sections extending longitudinally of the kiln chamber, each of said tiring sections having means for introducing gases into said kiln chamber in a transverse direction substantiaily tangentially to said wall means and at a velocity to cause circulation or" said gases in a transverse region along the wall means and around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, and means `associated with each gas introducing means for adjusting the same to introduce gases into the l@ kiln chamber at a selected temperature within a range of temperatures whereby each of said firing sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber at the tiring section location.

3. A continuous kiln comprising refractory Wall means defining a horizontally extending kiln chamber, a heat-up zone defined by a irst portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent tiring sections extending longitudinally of the kiln chamber, a soak zone deiined by a second longitudinal portion of said wall means and comprising at least one firing section extending longitudinally of the kiln chamber, each of said tiring sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, and means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said tiring sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber at the tiring section location, said gas introducing means in said heat-up and soak zones comprising a pair of burner assemblies, one of said burner assemblies being located to direct a gas stream tangentially into the upper portion of said kiln chamber, the other of said burner assemblies being located to direct a gas stream tangentially into the lower portion of said kiln chamber in the same circumferential direction as said one burner assembly so that said burners provide supplementing gas streams.

4. A continuous kiln comprising refractory wall means dening a horizontally extending kiln chamber, a heat-up zone dehned by a first portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone deiined by a second longitudinal portion of said wall means and comprising at least one iiring section extending longitudinallly of the kiln chamber, each of said liring sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, and means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of .temperatures whereby each of said tiring sections along the length of said kiln chamber may be set to provide a desired ternperature condition within said kiln chamber at the tiring section location, each of said gas introducing means in said heat-up and soak zones comprising la pair of burner assemblies, one of said burner assemblies being located to direct a gas stream tangentially into the upper portion of said kiln chamber, the other of said burner assemblies being located to direct a gas stream tangentially into the lower portion of said kiln chamber in the same circumferential direction as said one burner assembly, each of said burner assemblies comprising a diusion chamber, a burner directing its products of combustion through said dilusion chamber and into said kiln chamber, and means for supplying air to said diffusion chamber in an amount to increase the mas-s velocity of the gas stream entering said kiln chamber to a rate to eiiect circulation thereof around the circumference of the kiln chamber whereby the temperature in each firing section is substantially the same from the top to the bottom thereof.

5. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone deined by a first portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone defined by a second longitudinal portion of said wall means and comprising at least one firing section extending longitudinally of the kiln chamber, each of said firing sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, and means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said firing sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber, said gas introducing means of each firing section comprising a pair of burner assemblies, each of said burner assemblies comprising a diffusion chamber, a burner directing its products of combustion through said diffusion chamber and into said kiln chamber, means for supplying fuel to said burner, means for supplying air to said diffusion chamber for mixture with the burner combustion products to increase .the mass velocity of the gas stream entering said kiln chamber, a throttle valve adjustable to regulate the amount of fuel supplied to said burner, and a throttle valve adjustable to regulate the amount of air supplied to said diffusion chamber.

6. A continuous kiln comprising wall means defining a horzontally extending kiln chamber, a heat-up zone defined by a first portion f said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinalty of the kiln chamber, a soak zone dened by a sec ond longitudinal portion of said wall means and comprising at least one firing section extending longitudinally of the kiln chamber, a cooling zone between said soak zone and the discharge end of the kiln chamber, said cooling zone being defined by a third longitudinal portion of said wall means and comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, each or" said firing sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said firing sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber, each of said gas introducing means including at least one burner assembly, each of said burner assemblies comprising a diffusion chamber, a burner directing its products of combustion through said diffusion chamber and into said kiln chamber, and means for supplying preheated air to said diffusion chamber to increase the mass velocity of the gas stream entering said kiln chamber, said air supply means being connected between a portion of said cooling zone in the vicinity of said soak zone for supplying preheated air from said cooling zone to said diffusion chamber.

7. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone defined by a first portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone defined by a second longitudinal portion of said wall means and comprising at least one firing section extending longitudinally of the kkiln chamber, n cooiing Zone between said soak zone and the discharge end of the kiln chamber,

said cooling zone being defined by a third longitudinal portion of said wall means and comprising .a plurality of adjacent firing sections extending longitudinally of the kiln chamber, each of said firing sections having means for introducing gases into said kiln chamber in a transverse direction substantially tangentially to said wall means and at a velocity to cause circulation of said gases in a transverse region along the wall means and around the periphery of said kiln chamber, means for conveying .ware to be heated longitudinally through said kiln chamber and through said zones, means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said tiring sections may be set to provide a desired temperature condition within said kiln chamber at the firing section location, and means for restricting gas fiow between said soak zone and said cooling zone.

8. A kiln as claimed in claim 7 wherein said fiow restricting means comprises a vertically extending baffle blocking fiow between said soak and cooling zones, said bafiie being mounted on said wall means between said soak and cooling zones and having a pair of side portions extending vertically along the sides of said wall means and a horizontal portion extending between said pair of side portions across the top of the kiln chamber.

9. A kiln as claimed in claim 7 wherein said flow restricting means comprises means maintaining a constant pressure in a plane between said soak zone and said cooling zone.

it). A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone defined by a first portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone defined by a second longitudinal portion of said wall means and comprising at least one firing section extending longitudinaliy of the kiln chamber, a cooling zone between said soak zone and the discharge end of the kiln chamber, said cooling zone being defined by a third longitudinal portion of said wall means and comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, each of said firing sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said firing sections may be set to provide a desired temperature condition within said kiln chamber at the firing section location, and means maintaining a constant pressure along a static flow plane extending vertically between said soak zone and said cooling zone whereby the fiow of gases between said soak and cooling zones is minimized, said last-mentioned means including means for exhausting gases from said heat-up zone at a rate to maintain said constant pressure at the soak zone side of said static flow plane and means for exhausting gases from said cooling zone at a rate to maintain said constant pressure at the cooling zone side of said static iiow piane.

1l. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone decooling zone being defined by a third longitudinal portion of said wall means and comprising a plurality of adjacent tiring sections extending longitudinally of the kiln chamber, each of said iiring sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said fu'ing sections may be set to provide a desired temperature condition within said kiln chamber at the iiring section location, and means maintaining a constant pressure along a static flow plane extending vertically between said soak zone and said cooling zone whereby the flow of gases between said soak and cooling zones is minimized, said last-mentioned means including a first blower for exhausting gases from said heat-up zone, means regulating the rate of said exhaust of said iirst blower, first pressure sensing means arranged to sense the pressure in said kiln chamber immediately adjacent the soak zone side of said static flow plane, iirst control means operatively connected to said regulating means for said exhaust of said first blower and responsive to the pressure sensed by said first sensing means to adjust said iirst blower exhaust regulating means to exhaust gases at a rate to maintain said constant pressure at said iirst pressure sensing location, a second blower for exhausting gases from said cooling zone, means regulating the rate of said exhaust of said second blower, second pressure sensing means arranged to sense the pressure in said kiln immediately adjacent the cooling zone side of said static ow plane, and second control means operatively connected to said regulating means for the exhaust of said second blower and responsive to the pressure sensed by said second sensing means to adjust said second blower exhaust regulating means to exhaust gases at a rate to maintain said constant pressure at said second pressure sensing location.

12. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a heat-up zone deiined by a irst portion of said wall means extending longitudinally of the kiln chamber, said heat-up zone adjacent the charging end of the kiln chamber comprising a plurality of adjacent firing sections extending longitudinally of the kiln chamber, a soak zone deiined by a second longitudinal portion of said wall means and adjacent the heat-up zone comprising `at least one ring section extending longitudinally of the kiln chamber, a cooling zone between said soak zone and the discharge end of the kiln lli chamber, said cooling zone being deined by a third longitudinal portion of said wall means and comprising a plurality of adjacent liring sections extending longitudinally oi' the kiln chamber, each of said tiring sections having means for introducing gases into said kiln chamber in a transverse direction to cause circulation of said gases in a transverse region along the wall means around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones, means associated with each gas introducing means for adjusting the same to introduce gases into the kiln chamber at a selected temperature within a range of temperatures whereby each of said tiring sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber at the tiring section location, means drawing gases from said cooling zone and supplying them directly to the gas introducing means of said heat-up and soak zones for introduction into said kiln chamber, means for exhausting gases from the chargin7 end of Said heat-up zone, and means drawing gases from said cooling zone and returning a portion of said withdrawn gases directly to said cooling zone and directly exhausting the remaining portion of said withdrawn gases.

13. A continuous kiln comprising wall means defining a horizontally extending kiln chamber, a zone extending longitudinally of the kiln chamber, said zone comprising a plurality of adjacent tiring sections extending longitudinally of the kiln chamber, each of said tiring sections having means for introducing gases into said kiln chamber in a transverse direction substantially tangentially to said Wall means and at a velocity to cause circulation of said gases in a transverse region along the wall means and around the periphery of said kiln chamber, means for conveying ware to be heated longitudinally through said kiln chamber and through said zones and means associated with each gas introducing means for adjusting the same to i11- troduce gases into the kiln chamber at a selected tempera ture within a range of temperatures whereby each of said tiring sections along the length of said kiln chamber may be set to provide a desired temperature condition within said kiln chamber at the tiring section location.

References Cited in the file of this patent UNITED STATES PATENTS 1,499,354 Dressler July 1, 1924 2,070,300 Smith Feb. 9, 1937 2,805,848 Guigon et al Sept. 10, 1957 2,899,189 Matis et al Aug. 11, 1959 FOREIGN PATENTS 503,613 France Apr. 11, 1939 

13. A CONTINUOUS KILN COMPRISING WALL MEANS DEFINING A HORIZONTALLY EXTENDING KILN CHAMBER, A ZONE EXTENDING LONGITUDINALLY OF THE KILN CHAMBER, SAID ZONE COMPRISING A PLURALITY OF ADJACENT FIRING SECTIONS EXTENDING LONGITUDINALLY OF THE KILN CHAMBER, EACH OF SAID FIRING SECTIONS HAVING MEANS FOR INTRODUCING GASES INTO SAID KILN CHAMBER IN A TRANSVERSE DIRECTION SUBSTANTIALLY TANGENTIALLY TO SAID WALL MEANS AND AT A VELOCITY TO CAUSE CIRCULATION OF SAID GASES IN A TRANSVERSE REGION ALONG THE WALL MEANS AND AROUND THE PERIPHERY OF SAID KILN CHAMBER, MEANS FOR CONVEYING WARE TO BE HEATED LONGITUDINALLY THROUGH SAID KILN CHAMBER AND THROUGH SAID ZONES AND MEANS ASSOCIATED WITH EACH GAS INTRODUCING MEANS FOR ADJUSTING THE SAME TO INTRODUCE GASES INTO THE KILN CHAMBER AT A SELECTED TEMPERATURE WITHIN A RANGE OF TEMPERATURES WHEREBY EACH OF SAID FIRING SECTIONS ALONG THE LENGTH OF SAID KILN CHAMBER MAY BE SET TO PROVIDE A DESIRED TEMPERATURE CONDITION WITHIN SAID KILN CHAMBER AT THE FIRING SECTION LOCATION. 